During vulcanization of a tire, one or more tire vulcanizing systems may be employed for use with a tire mold. A principal characteristic of certain vulcanization systems is to place a system of heating and ventilation at the heart of an electric vulcanization system and thus provide a heated medium. For example, in an electric press, after a green tire is charged in a mold, supply of a high-temperature and high-pressure heating medium (hereinafter “heating medium”) into a bladder (i.e., one formed from an elastic material such as butyl rubber) causes the bladder to expand and thereby engage an inner wall surface of the tire.
Referring to FIG. 1, an exemplary tire vulcanizing system 10 of this type is shown for vulcanizing a green tire P. System 10 includes a fluid-tight enclosure 12 that receives a supply of a pressurized heating medium (e.g., nitrogen gas). The enclosure has a cavity 14 formed by a pair of plates 16, 18 connected by a bladder 20 with an operating shaft 22 effecting axial movement of at least one plate (as shown, plate 16 is axially displaceable). A heater 24 having one or more heating elements 24a heats the heating medium. It is understood that heater 24 may be selected from any amenable heating means, including but not limited to resistors, induction elements and the like. A fan 26, driven by an ensemble of a rotor 30 and a stator 31 (together forming a motor), agitates the heating medium at a high speed ω with respect to heater 24 so that heat is supplied to the heating medium at a high heat exchange ratio. Both heater 24 and fan 26 are enveloped within cavity 14 and therefore immersed wholly in the heating medium.
Heater 24 is disposed in a fluid path that is in communication with both cavity 14 and at least one conduit 32 through which the heating medium is introduced into, and/or extracted from, cavity 14. The heating medium traverses heating elements 24a before egress along an exit path 26a from fan 26 into the fluid-tight enclosure. The delivery of the heating medium provides sufficient energy to bladder 20 for deep penetration of tread pattern elements of the tire mold (not shown) into tire P. Tire P is thereby heated to a vulcanizing temperature through bladder 20 and simultaneously pressed in a molding direction. Exemplary embodiments of such systems and demonstrations of their use are disclosed by co-owned EP Patent No. EP 0686492 for TYRE VULCANISATION BY SUPPLYING HEAT FROM THE INSIDE, filed 18 May 1995, and co-owned and co-pending PCT Publication No. WO2013/164282 for a CHAMBER FOR VULCANIZING THE INNER PORTION OF A TIRE AND INCLUDING A FAN, filed 26 Apr. 2013, the entire disclosures of which are incorporated by reference herein.
As further illustrated in FIG. 2, the heating medium is subject to rotation under the effect of relative movement imparted by fan 26. The heating fluid attains sufficient tangential speed Ω within the cavity so as to ensure a good thermal exchange with the internal surface of bladder 20. In order to ensure this advantageous thermal exchange, the heating medium exhibits a speed Ω (see FIG. 1) that derives the necessary vulcanization energy from heater 24 and delivers it to an internal surface of bladder 20.
As pressure changes during a cure cycle, it is contemplated that homogenization of the temperature through the entire volume of the enclosure can be effected. To determine and monitor thermal transfer between the heating medium and the molded tire across the bladder, fluid temperature would be ideally determined along an internal surface of the tire. While some vulcanization processes contemplate the capture of the temperature of a heating medium, sensors for such purposes are usually arranged exterior to the fluid-tight enclosure (e.g., being arranged in pipelines or supply lines for the heating medium).
Measuring fluid temperature along internal tire surfaces presents a complex and expensive challenge. Therefore, reliable and predictable detection and monitoring of the heating medium is demanded for the duration of time under which the heating medium remains under pressure. Such detecting and monitoring, effected within the fluid-tight enclosure, can translate into control of heat transmission to the tire through the heating medium and bladder.